Prior art patents related to the production of MnZn ferrite have not approached the development of proper ferrous iron content during the calcining and milling steps. The prior art has failed to recognize that ferrous iron content can be controlled during the calcining operation and especially during the length of the milling operation.
While the prior art teaches calcining, the prior art does not appear to recognize that the calcining ought to be done in an inert atmosphere such as nitrogen, as recognized in this disclosure.